In play-back and/or recording devices it is often necessary to move a tape in both a forward and reverse direction at fixed speeds which are closely controlled. Tape driving systems which generally accomplish this function usually comprise a capstan shaft and a mating pressing element (pressure roller) which drive the tape between them at a constant speed and unwind the tape from one reel (a supplying reel) while simultaneously a suitable driving torque is applied to another reel (a collecting reel) which collects the tape. Generally in play-back and/or recording devices the tape can be moved at a normal forward play speed, at a fast forward speed, and at a fast reverse (fast rewind) speed.
For the normal play speed the angular velocity of the tape collecting reel must be variable. Generally a speed reducing friction coupler is coupled to a motor driven flywheel and the variable angular velocity of the collecting reel is provided by the natural reduction in speed which occurs as the wound tape circumference becomes larger. For fast forward operation, the shaft of the collecting reel is driven at an increased speed while the pressing element is moved away from the capstan shaft. For fast rewind operation the supplying reel becomes a driving reel while the collecting reel is decoupled from its drive source simultaneously with moving the pressing element away from the capstan shaft.
Many systems implement the aforementioned modes of operation for tape playing devices. Generally these tape drive systems use one or two rotating flywheels for implementing all of these driving modes. These flywheels are selectively used as driving sources for the supplying and collecting reel shafts by selectively coupling various wheels to the circumferences of the flywheels. However, the aforementioned systems do not produce very flat tape playing devices which are extremely desirable for portable or automotive applications. Furthermore, these systems run the risk of misaligning the coupling wheels which couple the flywheels to the reel shafts.
Some prior systems utilize the flywheel which drives the capstan as a power source to drive the collecting and supplying reels. This is generally accomplished by a coupler disc which is coaxial with the flywheel and which provides a friction drive for the collecting and supplying reels. These systems greatly increase the height dimension of the total tape drive system since the flywheel, the friction coupler disc, and the capstan shaft are all stacked on top of each other. These systems also have a problem in obtaining the proper driving speed for the collecting and supplying reels.